Power storage device

ABSTRACT

An electrical double layer capacitor having an electrolyte-containing layer between a first polarizable electrode layer and a second polarizable electrode layer. An insulating adhesive portion adheres to a first current collector and a second current collector and extends around the first and second polarizable electrode layers and the electrolyte-containing layer. A thickness of the insulating adhesive portion is larger than a sum of thicknesses of the first and second polarizable electrode layers and the electrolyte-containing layer.

CROSS REFERENCE TO RELATED APPLICATIONS

The present application is a continuation of International application No. PCT/JP2016/061124, filed Apr. 5, 2016, which claims priority to Japanese Patent Application No. 2015-082234, filed Apr. 14, 2015, the entire contents of each of which are incorporated herein by reference.

FIELD OF THE INVENTION

The present invention relates to a power storage device.

BACKGROUND OF THE INVENTION

A power storage device described in Patent Document 1 includes a first internal electrode extended to a first end surface, a second internal electrode extended to a second end surface, and a separator disposed between the first internal electrode and the second internal electrode. A first external electrode electrically connected to the first internal electrode is disposed on the first end surface. A second external electrode electrically connected to the second internal electrode is disposed on the second end surface. An electrical double layer capacitor described in Patent Document 1 has an advantage that it can be mounted on a mounting substrate.

Patent Document 1: International Publication No. 2014/083919

SUMMARY OF THE INVENTION

There is a desire to lower equivalent series resistance (ESR) of the electrical double layer capacitor as described in Patent Document 1.

A main object of the present invention is to provide an electrical double layer capacitor having low ESR.

A power storage device according to the present invention includes a device body. The device body has first and second principal surfaces, first and second side surfaces, and first and second end surfaces. The first and second principal surfaces extend along a length direction and a width direction. The first and second side surfaces extend along the length direction and a thickness direction. The first and second end surfaces extend along the width direction and the thickness direction. The device body has a first internal electrode, a second internal electrode, an electrolyte-containing layer, and an insulating adhesive portion. The first internal electrode has a first current collector and a first polarizable electrode layer. In the first internal electrode, at least the first current collector is extended to the first end surface. The first polarizable electrode layer is provided on at least one of both surfaces of the first current collector. The second internal electrode has a second current collector and a second polarizable electrode layer. In the second internal electrode, at least the second current collector is extended to the second end surface. The second polarizable electrode layer is provided on at least one of both surfaces of the second current collector. The electrolyte-containing layer is provided between the first polarizable electrode layer and the second polarizable electrode layer. The insulating adhesive portion adheres to the first current collector and the second current collector and extends around the first and second polarizable electrode layers and the electrolyte-containing layer. A thickness of the insulating adhesive portion is larger than a sum of thicknesses of the first and second polarizable electrode layers and the electrolyte-containing layer. Thus, it is possible to shorten a distance between the first polarizable electrode layer and the second polarizable electrode layer, and ESR of the power storage device can be reduced.

In the power storage device according to the present invention, it is preferable that the device body includes a functional portion having the first and second internal electrodes and the electrolyte-containing layer and an outer layer portion provided around the functional portion and forming the first and second principal surfaces and the first and second side surfaces of the device body, and at least one central portion of the functional portion is depressed and forms a depressed portion between the functional portion and the outer layer portion.

In the power storage device according to the present invention, it is preferable that the first principal surface is flatter than a principal surface of the functional portion. In this case, for example, it is easy to take hold of the power storage device with a suction mounter or the like. In addition, since strength of the depressed portion of the power storage device can be further increased, the power storage device is less likely to be damaged, for example, when the power storage device is mounted.

It is preferable that the power storage device according to the present invention further includes a reinforcing member disposed in the depressed portion between the functional portion and the outer layer portion. In this case, strength of the power storage device can be further increased.

In the power storage device according to the present invention, a thickness of the functional portion at one of the first and second end surfaces is smaller than a thickness of the functional portion where the insulating adhesive portion is located. In this case, moisture or the like is less likely to enter the functional portion. Accordingly, deterioration of the power storage device due to moisture can be suppressed.

The present invention can provide an electrical double layer capacitor having low ESR.

BRIEF EXPLANATION OF THE DRAWINGS

FIG. 1 is a schematic perspective view of a power storage device according to a first embodiment.

FIG. 2 is a schematic cross-sectional view taken along line II-II of FIG. 1.

FIG. 3 is a schematic cross-sectional view of the power storage device according to the first embodiment excluding first and second external electrodes.

FIG. 4 is a schematic cross-sectional view of a power storage device according to a second embodiment excluding first and second external electrodes.

FIG. 5 is a schematic cross-sectional view of a power storage device according to a variation 1 excluding first and second external electrodes.

DETAILED DESCRIPTION OF THE INVENTION

Hereinafter, a description will be given of an example of a preferred embodiment of the present invention. However, the following embodiments are provided merely by way of example. The present invention is not limited to the following embodiments.

Throughout the drawings to which the embodiments and the like refer, elements having substantially the same functions will be referred to by the same reference symbols. The drawings to which the embodiments and the like refer are schematically illustrated. The dimensional ratios and the like of objects illustrated in the drawings may be different from those of the actual objects. Different drawings may have different dimensional ratios and the like of the objects. Dimensional ratios and the like of specific objects should be determined in consideration of the following descriptions.

First Embodiment

FIG. 1 is a schematic perspective view of a power storage device according to this embodiment. FIG. 2 is a schematic cross-sectional view taken along line II-II of FIG. 1. FIG. 3 is a schematic cross-sectional view of the power storage device according to the first embodiment excluding first and second external electrodes.

A power storage device 1 shown in FIGS. 1 to 3 is, for example, one of an electrical double layer capacitor and a device constituting a secondary battery.

The power storage device 1 includes a device body 10. The device body 10 has first and second principal surfaces 10 a and 10 b, first and second side surfaces 10 c and 10 d, and first and second end surfaces 10 e and 10 f. The first and second principal surfaces 10 a and 10 b extend along a length direction L and a width direction W, respectively. The first principal surface 10 a and the second principal surface 10 b face each other in a thickness direction T. The first and second side surfaces 10 c and 10 d extend along the length direction L and the thickness direction T, respectively. The first side surface 10 c and the second side surface 10 d face each other in the width direction W. Each of the first and second end surfaces 10 e and 10 f extends along the width direction W and the thickness direction T. The first end surface 10 e and the second end surface 10 f face each other in the length direction L. In the present embodiment, the device body 10 is provided in a substantially rectangular parallelepiped shape.

As shown in FIG. 2, the device body 10 has a plurality of first internal electrodes 11 and a plurality of second internal electrodes 12. The first and second internal electrodes 11 and 12 are alternately provided along the thickness direction T.

The first internal electrode 11 is provided in parallel with the first and second principal surfaces 10 a and 10 b. At least a part of the first internal electrode 11 is extended to the first end surface 10 e. Specifically, in this embodiment, a first current collector 11 a, which will be described later, of the first internal electrode 11 is extended to the first end surface 10 e. The first internal electrode 11 is not extended to the second end surface 10 f and the first and second side surfaces 10 c and 10 d.

The first internal electrode 11 has a first current collector 11 a and a first polarizable electrode layer 11 b. The first polarizable electrode layer 11 b is provided on at least one of the first current collectors 11 a. In this embodiment, the first polarizable electrode layer 11 b is provided on one surface of the first current collector 11 a.

The first current collector 11 a can be constituted by a metal foil formed of at least one metal such as aluminum and copper.

The first polarizable electrode layer 11 b preferably contains a carbon material such as activated carbon.

The second internal electrode 12 is provided in parallel with the first and second principal surfaces 10 a and 10 b. At least a part of the second internal electrode 12 is extended to the second end surface 10 f. Specifically, in this embodiment, at least a second current collector 12 a of the second internal electrode 12 is extended to the second end surface 10 f. The second internal electrode 12 is not extended to the first end surface 10 e and the first and second side surfaces 10 c and 10 d.

The second internal electrode 12 has a second current collector 12 a and a second polarizable electrode layer 12 b. The second polarizable electrode layer 12 b is provided on the surface of at least one side of the second current collector 12 a. In this embodiment, the second polarizable electrode layer 12 b is provided on one surface of the second current collector 12 a.

The second current collector 12 a can be constituted by a metal foil formed of at least one metal such as aluminum and copper.

In this case, the second polarizable electrode layer 12 b preferably contains a carbon material such as activated carbon.

An electrolyte-containing layer 13 is provided between the first polarizable electrode layer 11 b and the second polarizable electrode layer 12 b. The first polarizable electrode layer 11 b and the second polarizable electrode layer 12 b face each other with the electrolyte-containing layer 13 interposed therebetween.

The electrolyte-containing layer 13 contains an electrolyte. The electrolyte-containing layer 13 is preferably formed of a gel containing an electrolyte. As the gel, for example, high polymer polyethylene oxide resin or the like can be used.

The device body 10 has a functional portion 10A and a casing 10B. The functional portion 10A is a portion that exhibits a function as a power storage device. The functional portion 10A includes the first and second internal electrodes 11 and 12 and the electrolyte-containing layer 13 described above.

The casing 10B covers a portion of an outer surface of the functional portion 10A. Specifically, the casing 10B covers first and second principal surfaces and first and second side surfaces of the functional portion 10A. First and second end surfaces of the functional portion 10A are exposed from the casing 10B. Accordingly, the first and second principal surfaces 10 a and 10 b and the first and second side surfaces 10 c and 10 d are constituted by the casing 10B. The first and second end surfaces 10 e and 10 f are constituted by the functional portion 10A and the casing 10B.

A first external electrode 18 is provided on the first end surface 10 e. The first external electrode 18 is electrically connected to the first internal electrode 11. The first external electrode 18 has a first electrode film 18 a and a first metal cap 18 b.

The first electrode film 18 a is connected to the first internal electrode 11. The first electrode film 18 a is provided so as to cover the first end surface 10 e. Specifically, the first electrode film 18 a covers substantially the entire first end surface 10 e. The first electrode film 18 a is not located on the first and second principal surfaces 10 a and 10 b and the first and second side surfaces 10 c and 10 d.

The first metal cap 18 b covers a portion on the first end surface 10 e side of the device body 10. Specifically, the first metal cap 18 b covers the first end surface 10 e and partially covers the first and second principal surfaces 10 a and 10 b and the first and second side surfaces 10 c and 10 d on the first end surface 10 e side.

The first metal cap 18 b is electrically connected to the first electrode film 18 a.

A second external electrode 19 is provided on the second end surface 10 f. The second external electrode 19 is electrically connected to the second internal electrode 12. The second external electrode 19 has a second electrode film 19 a and a second metal cap 19 b.

The second electrode film 19 a is connected to the second internal electrode 12. The second electrode film 19 a is provided so as to cover the second end surface 10 f. Specifically, the second electrode film 19 a is provided so as to cover substantially the entire second end surface 10 f. The second electrode film 19 a is not located on the first and second principal surfaces 10 a and 10 b and the first and second side surfaces 10 c and 10 d.

The second metal cap 19 b covers a portion on the second end surface 10 f side of the device body 10. Specifically, the second metal cap 19 b covers the second end surface 10 f and partially covers the first and second principal surfaces 10 a and 10 b and the first and second side surfaces 10 c and 10 d on the second end surface 10 f side.

The second metal cap 19 b is electrically connected to the second electrode film 19 a.

In this embodiment, each of the first and second electrode films 18 a and 19 a is formed of a sprayed film. The first and second electrode films 18 a and 19 a can be formed of, for example, Al, an Al alloy, or the like.

Each of the first and second metal caps 18 b and 19 b may be formed of, for example, an Fe—Ni alloy, a Cu—Zn alloy, a Cu—Zn—Ni alloy, Al or the like. A plating film may be provided on outer surfaces of the first and second metal caps 18 b and 19 b. The plating film may be, for example, an Ni/Ag plating film, an Ni/Au plating film, an Ni/Sn plating film, or the like.

In the power storage device 1, as shown in the following formula (1), a thickness of an insulating adhesive portion 15 is larger than the sum of thicknesses of the first and second polarizable electrode layers 11 b and 12 b and the electrolyte-containing layer 13.

a>b1+b2+c  (1)

a: the thickness of the insulating adhesive portion

b1: the thickness of the first polarizable electrode layer 11 b

b2: the thickness of the second polarizable electrode layer 12 b

c: the thickness of the electrolyte-containing layer 13

Thus, it is possible to shorten a distance between the first polarizable electrode layer 11 b and the second polarizable electrode layer 12 b. Accordingly, the ESR of the power storage device 1 can be reduced.

From the viewpoint of further reducing the ESR of the power storage device 1, it is preferable that the thickness of the insulating adhesive portion 15 is 1.1 times or more the thicknesses of the first and second polarizable electrode layers 11 b and 12 b and the electrolyte-containing layer 13. However, if the thickness of the insulating adhesive portion 15 is too large, an outer portion of the device body 10 in the length direction L tends to be largely bent, and at times the current collector tends to be ruptured in the bent portion. Accordingly, it is preferable that the thickness of the insulating adhesive portion 15 is 1.3 times or less the thicknesses of the first and second polarizable electrode layers 11 b and 12 b and the electrolyte-containing layer 13.

As described above, in this embodiment, the thickness of the insulating adhesive portion 15 is larger than the thicknesses of the first and second polarizable electrode layers 11 b and 12 b and the electrolyte-containing layer 13. Thus, as shown in FIG. 3, at least one of central portions of first and second principal surfaces 10A1 and 10A2 of the functional portion 10A is depressed. Specifically, in this embodiment, the central portions of both the first and second principal surfaces 10A1 and 10A2 are depressed. The first principal surface 10 a is flatter than the first principal surface 10A1. The first principal surface 10 a is substantially a flat surface. The second principal surface 10 b is flatter than the second principal surface 10A2. The second principal surface 10 b is substantially a flat surface. Thus, for example, when the power storage device 1 is mounted, it is easy to take hold of the power storage device 1 with a suction mounter or the like.

Between the casing 10B and the functional portion 10A, a reinforcing member 10C is disposed in the depressed portion. Strength of the power storage device 1 is increased by the reinforcing member 10C. Accordingly, when the power storage device 1 is mounted using a mounter, the power storage device 1 is less likely to be damaged.

The reinforcing member 10C can be formed of, for example, a thermosetting resin, such as a polyimide resin, an epoxy resin, and a phenol resin, or the like. Among them, the epoxy resin is preferably used as the reinforcing member 10C.

When the central portion of the principal surface of the functional portion having a rectangular parallelepiped shape is depressed, an end portion of the functional portion usually widens, and an area of the end surface increases. Thus, moisture tends to intrude from the end surface to the functional portion. On the other hand, as shown in FIG. 2, in the power storage device 1, the electrolyte-containing layer 13 is not provided outside the insulating adhesive portion 15. Thus, as shown in FIG. 3, when the distance between the first polarizable electrode layer 11 b and the second polarizable electrode layer 12 b is short, and thicknesses at the first and second end surfaces 10 e and 10 f of the functional portion 10A are smaller than a thickness of a portion of the functional portion 10A where the insulating adhesive portion 15 is provided, the areas of the first and second end surfaces 10 e and 10 f of the functional portion 10A are small. Accordingly, it is possible to simultaneously realize reduction in ESR and suppression of intrusion of moisture from the first and second end surfaces 10 e and 10 f into the functional portion 10A. Thus, in the power storage device 1 with reduced ESR, deterioration due to moisture is effectively suppressed.

From the viewpoint of more effectively suppressing the deterioration of the power storage device 1 due to moisture, the thicknesses at the first and second end surfaces 10 e and 10 f of the functional portion 10A are preferably 0.9 times or less the thickness of the portion of the functional portion 10A where the insulating adhesive portion 15 is provided. However, if the thicknesses at the first and second end surfaces 10 e and 10 f of the functional portion 10A are too small, an outer portion of the functional portion 10A in the length direction L tends to be largely bent, and at times the current collector tends to be ruptured in the bent portion. Accordingly, the thicknesses at the first and second end surfaces 10 e and 10 f of the functional portion 10A are preferably 0.8 times or more the thickness of the portion of the functional portion 10A where the insulating adhesive portion 15 is provided.

Hereinafter, a description will be given of another example of a preferred embodiment of the present invention. In the following description, members having substantially the same functions as those of the first embodiment will be referred to using the same symbols and description thereof will be omitted.

Second Embodiment

FIG. 4 is a schematic cross-sectional view of a power storage device according to the second embodiment excluding first and second external electrodes.

In the first embodiment, an example in which the central portions of both the first and second principal surfaces 10A1 and 10A2 of the functional portion 10A are depressed has been described. However, the present invention is not limited to this configuration. For example, the central portion of only one of the first and second principal surfaces 10A1 and 10A2 may be depressed.

Variation 1

FIG. 5 is a schematic cross-sectional view of a power storage device according to the variation 1 excluding first and second external electrodes.

In the first and second embodiments, an example in which the reinforcing member 10C is disposed only in the depressed portion has been described. However, the present invention is not limited to this configuration. For example, as shown in FIG. 5, the reinforcing member 10C may be disposed outside the insulating adhesive portion 15 in addition to the inside of the depressed portion.

Variation 2

In the first and second embodiments, an example in which the reinforcing member 10C is disposed in the depressed portions of the principal surfaces 10A1 and 10A2 of the functional portion 10A has been described. However, the present invention is not limited to this configuration. In the present invention, for example, the depressed portion of the principal surface of the functional portion may be filled with the casing.

DESCRIPTION OF REFERENCE SYMBOLS

1: Power storage device

10: Device body

10A: Functional portion

10A1: First principal surface of functional portion

10A2: Second principal surface of functional portion

10B: Casing

10 a: First principal surface

10 b: Second principal surface

10 c: First side surface

10 d: Second side surface

10 e: First end surface

10 f: Second end surface

10C: Reinforcing member

11: First internal electrode

11 a: First current collector

11 b: First polarizable electrode layer

12: Second internal electrode

12 a: Second current collector

12 b: Second polarizable electrode layer

13: Electrolyte-containing layer

14: Adhesive layer

15: Insulating adhesive portion

18: First external electrode

18 a: First electrode film

18 b: First metal cap

19: Second external electrode

19 a: First electrode film

19 b: Second metal cap 

1. A power storage device comprising: a device body having first and second principal surfaces extending along a length direction and a width direction, first and second side surfaces extending along the length direction and a thickness direction, and first and second end surfaces extending along the width direction and the thickness direction, the device body comprising: a first internal electrode which has a first current collector and a first polarizable electrode layer on at least one surface of the first current collector and the first current collector extends to the first end surface, a second internal electrode which has a second current collector and a second polarizable electrode layer on at least one surface of the second current collector and the second current collector extends to the second end surface, an electrolyte-containing layer between the first polarizable electrode layer and the second polarizable electrode layer, and an insulating adhesive portion adhered to the first current collector and the second current collector and extending around the first and second polarizable electrode layers and the electrolyte-containing layer, wherein a thickness of the insulating adhesive portion is larger than a sum of thicknesses of the first and second polarizable electrode layers and the electrolyte-containing layer.
 2. The power storage device according to claim 1, wherein the device body has a functional portion comprising the first and second internal electrodes and the electrolyte-containing layer, and an outer layer portion surrounding the functional portion and forming the first and second principal surfaces and the first and second side surfaces of the device body, wherein at least one central portion of the functional portion is depressed and forms a depressed portion between the functional portion and the outer layer portion.
 3. The power storage device according to claim 2, wherein the first principal surface of the device body is flatter than a principal surface of the functional portion.
 4. The power storage device according to claim 3, further comprising a reinforcing member disposed in the depressed portion between the functional portion and the outer layer portion.
 5. The power storage device according to claim 4, wherein the reinforcing member comprises a thermosetting resin, an epoxy resin, or a phenol resin.
 6. The power storage device according to claim 2, wherein a thickness of the functional portion at one of the first and second end surfaces is smaller than a thickness of the functional portion where the insulating adhesive portion is located.
 7. The power storage device according to claim 6, wherein the thicknesses of the functional portion at the one of the first and second end surfaces is 0.8 to 0.9 times the thickness of the functional portion where the insulating adhesive portion is located.
 8. The power storage device according to claim 1, wherein the device body has a functional portion comprising the first and second internal electrodes and the electrolyte-containing layer, and an outer layer portion surrounding the functional portion and forming the first and second principal surfaces and the first and second side surfaces of the device body, wherein opposed central portions of the functional portion are depressed and form depressed portions between the functional portion and the outer layer portion.
 9. The power storage device according to claim 8, wherein the first principal surface of the device body is flatter than a principal surface of the functional portion.
 10. The power storage device according to claim 9, further comprising a reinforcing member disposed in the depressed portion between the functional portion and the outer layer portion.
 11. The power storage device according to claim 10, wherein the reinforcing member comprises a thermosetting resin, an epoxy resin, or a phenol resin.
 12. The power storage device according to claim 8, wherein a thickness of the functional portion at one of the first and second end surfaces is smaller than a thickness of the functional portion where the insulating adhesive portion is located.
 13. The power storage device according to claim 12, wherein the thicknesses of the functional portion at the one of the first and second end surfaces is 0.8 to 0.9 times the thickness of the functional portion where the insulating adhesive portion is located.
 14. The power storage device according to claim 1, wherein the thickness of the insulating adhesive portion is 1.1 to 1.3 times the thicknesses of the first and second polarizable electrode layers and the electrolyte-containing layer.
 15. The power storage device according to claim 1, further comprising: a first external electrode on the first end surface and electrically connected to the first internal electrode; and a second external electrode on the second end surface and electrically connected to the second internal electrode. 